The submandibular gland is one of the major salivary glands, the other 2 being the parotid and sublingual salivary glands. Unfortunately stones can develop in the duct that drains the submandibular gland and as a result can block the outflow to the gland.
Classically the patient complains of pain under the jaw in association with eating food and this area may swell because of the obstruction to normal saliva into the mouth. The stones are radioopaque usually therefore, they can be demonstrated on a simple XRay or an Ultrasound.
Occasionally these stones may pass into the mouth through the duct opening under the tongue. If the stones are troublesome and located in the floor of mouth then they can be removed there. If the stones are based further back and symptomatic it is better to remove the duct as an excision of the submandibular gland.